cfherrman
TFP Guide
"Adjusted TA" calculation needed for PH stabilization
- Thread starter Drd
- Start date
Just so I'm clear - TFP recommendations refer to measured TA?
E.g. for my pool it recommends TA 60-80
So that's the raw reading, which will include a certain proportion of CYA alkalinity?
If so, then TFP is recommending TA levels about 50% of the recommendation of an Adjusted TA of 80-120?
E.g. for my pool it recommends TA 60-80
So that's the raw reading, which will include a certain proportion of CYA alkalinity?
If so, then TFP is recommending TA levels about 50% of the recommendation of an Adjusted TA of 80-120?
Measured TA. Use Pool Math and it will figure everything else behind the scenes.
The feed back has been great and I appreciate it very much. I am coming to understand the CSI and calculator as a whole much better than I did initially. But I still have some questions. First I do realize there is initial rise in PH after adding chlorine to the pool water. I test in the morning to only find out how much chlorine was added via my feeder & pump running overnight and if it's sufficient. Second I test for TA and PH at the end of the day when I will get a truer test result along with the chlorine again so I can determine how much chlorine is being depleted to gage if my FC level is at least at the min. level when swimming is most likely so I can adjust the feeder.
OK so what I'm understanding is that the pool math does factor into it's CSI calculations CYA adjustments to TA when the "Now" stated for CYA is over 30ppm to obtain the "Carbonate Total Alkalinity" automatically. That's good to know, although it is not stated so in the description of the CSI calculations on Pool Math. The point I am having a hard time with is why if CSI results, which is apparently what most people are concerned with as representative of being "Balanced", the "Adjusted TA" part is being portrayed as non important then. Additionally I can't get my head around why if the CSI factors in the calculations for the True Total Alkalinity based on CYA to make adjustments to balance your pool water why can't you just adjust your TA or CYA level to accomplish the same thing if it will help with the PH and lessening the addition of acid upfront. These concepts are hard to follow. I just have a hard time with the idea that I am glued to the pool with acid and I can't improve my maintenance level even in Arizona where there are more pools per capita than most other states. I have come to the realization that the high Calcium (hard water) presently over 600ppm and high CYA levels I have are major factors in my problems because that contributes to the "Carbonate" which effect alkalinity that effects PH. The Taylor manual CSI calculator, Watergram" that comes with the 2006C test kit does require you to adjust the TA by CYA by 1/3 to find the correct CSI values. The bottom line is this value is subjective to what all the other tests results are stated allowing you to adjust each of the individual levels in order to reach a CSI in a good range so you know where and how much you want to make adjustments with acid etc to reach that goal/CSI value.
Can I please get a layman's (for dummies) explanation as to why I should not believe that increasing my TA ppm just like you do the chlorine ppm to compensate for the excess CYA would not be a logical adjustment as I am already getting encouragement to do?
OK so what I'm understanding is that the pool math does factor into it's CSI calculations CYA adjustments to TA when the "Now" stated for CYA is over 30ppm to obtain the "Carbonate Total Alkalinity" automatically. That's good to know, although it is not stated so in the description of the CSI calculations on Pool Math. The point I am having a hard time with is why if CSI results, which is apparently what most people are concerned with as representative of being "Balanced", the "Adjusted TA" part is being portrayed as non important then. Additionally I can't get my head around why if the CSI factors in the calculations for the True Total Alkalinity based on CYA to make adjustments to balance your pool water why can't you just adjust your TA or CYA level to accomplish the same thing if it will help with the PH and lessening the addition of acid upfront. These concepts are hard to follow. I just have a hard time with the idea that I am glued to the pool with acid and I can't improve my maintenance level even in Arizona where there are more pools per capita than most other states. I have come to the realization that the high Calcium (hard water) presently over 600ppm and high CYA levels I have are major factors in my problems because that contributes to the "Carbonate" which effect alkalinity that effects PH. The Taylor manual CSI calculator, Watergram" that comes with the 2006C test kit does require you to adjust the TA by CYA by 1/3 to find the correct CSI values. The bottom line is this value is subjective to what all the other tests results are stated allowing you to adjust each of the individual levels in order to reach a CSI in a good range so you know where and how much you want to make adjustments with acid etc to reach that goal/CSI value.
Can I please get a layman's (for dummies) explanation as to why I should not believe that increasing my TA ppm just like you do the chlorine ppm to compensate for the excess CYA would not be a logical adjustment as I am already getting encouragement to do?
Because the higher the TA the faster pH rises. As has been pointed out above, you can never stop pH rise, only slow it down.
Because CYA and TA are the hardest two things to adjust. Raising TA is easy, just toss in some baking soda. But, as I said above the higher the TA the faster pH rises. Lowering TA requires a system of lowering both pH & TA with acid and then just raising the pH back up whit aeration, repeat as necessary. CYA can only be lowered with water exchange or an RO treatment.
You have been dealt a bad hand. Your fill water is high TA and high CH.....
- May 23, 2015
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I’m going to assume you have a plaster pool as it is not clear in your signature and most pools in AZ are plaster construction. For a plaster pool, you want your CSI to be between -0.3 and 0 as that reduces the calcium scaling potential which shows up as white scale on your tile and calcium scale inside heaters and SWG cells (which you do not have).
Factors that affect CSI -
pH - increasing pH makes CSI more positive, lowering pH makes CSI more negative
TA - increasing TA makes CSI more positive while lowering it makes CSI more negative
CH - increasing CH makes CSI more positive while lowering CH makes CSI more negative
CYA - increasing CYA makes CSI more negative while lower CYA makes CSI more positive
Salt - increasing salinity makes CSI more negative while lower salinity makes CSI more positive
Temp - higher water temps make CSI more positive while lower water temps makes CSI more negative
Borates - Increasing borates makes CSI more negative while decreasing borates makes CSI more positive
Of all the chemical levels that you can choose from, adjusting pH/TA has the greatest impact on CSI and doing so is easily reversible if you overshoot. Changing any other parameter is more difficult or results in a permanent chemical additions that can not be easily undone.
CYA and CH have nothing to do with carbonates. CYA adds no carbonates to the water. Soluble calcium ions occur mostly as calcium chloride or calcium hydroxide as calcium carbonate is an insoluble precipitate at normal water pH (7-8 range).
As for increasing TA to reduce acid use, that is the exact opposite of what will happen. When you increase TA, you primarily do that by adding baking soda (sodium bicarbonate) to the water. Doing so increases the concentration of dissolved inorganic carbon (bicarbonate ion, HCO3-) which then will increase the concentration of dissolved CO2 in the water (because bicarbonate and aqueous CO2 are always in equilibrium with one another). Once you increase the amount of dissolved CO2 in the water, you increase the rate of outgassing of CO2 because the concentration of CO2 in the water is higher than the concentration of CO2 in the atmosphere right above the waters surface. When CO2 leaves water, there is a chemical reaction from the bicarbonate ion that tries to restore the balance of CO2/HCO3- in the water and that chemical reaction uses up a hydrogen ion. That reaction thus increases pH. It’s a complicated series of chemical reaction but that is how the water/CO2 chemistry works and it is why surface waters have much higher pH than deep ground water. It is this complicated water/CO2 cycle that drives a lot of atmospheric/ocean chemistry changes. In the tiny ecosystem of a residential pool, it is the water/CO2 cycle that causes almost all pH changes.
So yes, acid additions are just something you have to deal with. Adding more TA to your pool with bicarbonate only makes the situation worse, not better. Adding water to your pool that has high TA makes the situation worse, not better. That’s life with a pool in the western desert. You can lower TA and add borates to make the pH more stable, but it’s not going to change the total amount of acid you have to add, just the frequency with which you add it. Sorry, I know it seems like it shouldn’t be that way, but it is. When other pool owners say they never adjust pH it’s either because they live in an area where the fill water adds minimal alkalinity to the pool, or they use acidic forms of chlorine that keep the TA/pH low, or they just don’t test and understand their water very well....or, they higher a pool maintenance company and just never think about it.
I realize now I have other factors at play given I have a play pool that is only 5 ft deep at the most so water temperature is warmer (about 75-82 right now-nice) and granted more surface area per gallon than a regular pool of similar size -10,000 gals. I have an interesting change to report (actually I was spurred to check my CYA today based on one of the above posts on what effects or depletes CYA). As I stated previously, my FC was zero for a couple of days, so I thought I should test and see if there was any changed to my CYA level of 90ppm and I can happily report is has lowered to 70ppm - Yeah! and I tested it twice too. You know, now it makes sense when I read posts were they talked about their pool that was closed for the winter had lower CYA levels when they re-openned their pool. May not be a recommended method to reduce CYA levels but non the less that is the outcome.
My FC level has been steady but we just had some rain today and my PH which was 7.8 for the last couple of days just tested at 8.0 now so I will add some acid. Although my city water tests at 100pm TA, the water test around 80ppm-90ppm due to adding acid for ph. I can't say lowering TA to 60ppm worked for me as it bounced right back up to 8.0 very quickly, so I just wasted all that acid but at least I tried it out to see.
I still find the CYA/TA theory. if you will, an interesting topic, but I will not pursue any further discussion and I thank everyone for their feedback and the time they took to provide such detailed responses. You definitely are passionate about water chemistry and helping others with their pool issues and I know you have helped many people. Till the next time!
P.S. I would like to know if someone knows of a reliable mechanical digital tester that produces accurate results as a replacement for chemicals. it would be so much easier to just read the digital numeric results.
My FC level has been steady but we just had some rain today and my PH which was 7.8 for the last couple of days just tested at 8.0 now so I will add some acid. Although my city water tests at 100pm TA, the water test around 80ppm-90ppm due to adding acid for ph. I can't say lowering TA to 60ppm worked for me as it bounced right back up to 8.0 very quickly, so I just wasted all that acid but at least I tried it out to see.
I still find the CYA/TA theory. if you will, an interesting topic, but I will not pursue any further discussion and I thank everyone for their feedback and the time they took to provide such detailed responses. You definitely are passionate about water chemistry and helping others with their pool issues and I know you have helped many people. Till the next time!
P.S. I would like to know if someone knows of a reliable mechanical digital tester that produces accurate results as a replacement for chemicals. it would be so much easier to just read the digital numeric results.
cfherrman
TFP Guide
A pH tester that you calibrate often is about it. There is a Taylor lab thing that works alright I think
I'll google it up, thanks.
Additionally, I would like to mention on Page 14 of Taylor Water Chemistry guide booklet (part #2004B) provided with the Taylor water test kit 2006C includes a paragraph titled "Cyanuric Acid Correction to Total Alkalinity". The formula stated is Alkc = Alkta - (measured CYA x 0.33). Which simply states TA measures all forms of alkalinity (aka Total Aklinity) including Carbonate Alkalinity and Cyanurate Alkalinity present in the water sample. Since "water balance" calculations (Saturated Index I believe they mean) ONLY USE THE CARBONATE ALKALINITY PORTION, a correction (which varies with PH) should be applied to compensate for the CYA alkalinity portion. For most waters "within" the recommended ph and CYA acid levels, using this factor is only within experimental error (not needed I assume they mean).
This final Note is what I found most helpful to me in understanding the confusion I'm experiencing; "While Taylor Technologies recommends using the correction, some members of the pool/spa industry question it's value" and I can validate that is a true and correct statement. I'm just the type that keeps an open mind and absorbs all information as valuable for the best possible outcome and right now that's controlling and or balancing my water taking in all various factors I have learned here and from others who have offered their time and knowledge to help me learn how to care for my pool myself at the prime age of 65....never say your too old to learn!
Additionally, I would like to mention on Page 14 of Taylor Water Chemistry guide booklet (part #2004B) provided with the Taylor water test kit 2006C includes a paragraph titled "Cyanuric Acid Correction to Total Alkalinity". The formula stated is Alkc = Alkta - (measured CYA x 0.33). Which simply states TA measures all forms of alkalinity (aka Total Aklinity) including Carbonate Alkalinity and Cyanurate Alkalinity present in the water sample. Since "water balance" calculations (Saturated Index I believe they mean) ONLY USE THE CARBONATE ALKALINITY PORTION, a correction (which varies with PH) should be applied to compensate for the CYA alkalinity portion. For most waters "within" the recommended ph and CYA acid levels, using this factor is only within experimental error (not needed I assume they mean).
This final Note is what I found most helpful to me in understanding the confusion I'm experiencing; "While Taylor Technologies recommends using the correction, some members of the pool/spa industry question it's value" and I can validate that is a true and correct statement. I'm just the type that keeps an open mind and absorbs all information as valuable for the best possible outcome and right now that's controlling and or balancing my water taking in all various factors I have learned here and from others who have offered their time and knowledge to help me learn how to care for my pool myself at the prime age of 65....never say your too old to learn!
- May 23, 2015
- 24,629
- Pool Size
- 16000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
First, let me say that Pool Math already takes all of these factors into consideration when calculating CSI so that the user does not have to have look-up tables for alkalinity corrections. Pool Math also adjusts values for temperature and ionic strength (via salinity measurement). This is all done in the website programming.
Second point - any discussion of saturation indices gets complicated because saturation indices were originally developed for the water boiler and steam generator industries. The original Langlier Saturation Index (LSI) was developed in the 1940’s and based on a lot of empirical data from lake and reservoir waters. It used a number of look-up tables with correction values and offset constants to make the models fit the existing data. It did not use “first principles” chemistry to derive its formula but rather interpolated data. Once the chemistry was more sufficiently advanced and better thermodynamic values of fundamental chemical reactions were measured, the LSI was revised and updated along the way (mainly in how the various constants were affected by ionic strength). Applying it to pool water did not make a lot of practical sense because pools are open chemical systems (water is in contact with the atmosphere) and pool water has much higher TDS and chemicals in it (like cyanurates) that will affect alkalinity and pH. But, people in the industry took the LSI formulation and added ever more correction factors onto it to “make it work.” The CSI that TFP uses was developed by a chemical engineer where the actual saturation values of calcite in pool water are derived from first principles and chemical thermodynamics. This makes the CSI a more obvious (if one is interested in the chemistry) representation of the saturation because all of its components relate to some chemical thermodynamic treatment rather than using a lot of “fudge factors” and look-up tables.
At the end of the day it does not entirely matter which saturation index you use as they both will lead you in the same direction. What is important to understand is the role of carbonate alkalinity in pH rise which is something most of the industry gets completely wrong. If you raise TA with bicarbonate additions you will increase the carbonate alkalinity concentration and you will make pH rise faster as well as require more acid to lower it. That is simple, proven chemistry that is not at all remarkable and yet, with consistent ignorance, the industry (and many resources in the internet) gets it wrong over and over again.
I get somewhat confused when I try to understand your explanations and I certainly don't want to cause you any irritation but I probably am, sorry, but in the beginning you say Pool Math does this correction behind the scenes automatically, but in the next statement you staunchly dismiss the need for the correction and that it's just some old junk science from a different time period and water application. I just don't understand all the other various scientific pool water analysis; such as another one I just found on the subject at http://www.aquaticspecialtyservices.com/msds/techbulletin2.pdf which is nothing but about testing pool/spa water and the accuracy of SI calculations which is the true indicator your water is "Balanced" to avoid damage to your pool which is a critical aspect of pool water maintenance. Water is water and this correction being discussed is specifically addresses high levels of CYA in stabilized pools due to usage of Chorline Tablets in CYA build up over time and once it reaches a high concentration in combination with a certain PH level, it produces a TA test result that in fact has changed composition, therefore not truly accurate when it is used to determine the SI level and will produce a false SI "balanced" result. This basically says, if you have very high levels of CYA in your pool water when your ph is 7.2-7.8, a chemical change occurs where the CA, "cyanurate acid", replaces the carbonate in Alkalinity and increasing levels of CA as much as 73% to 83% of the TA test result depending on the PH levels. This is then being used to calculate the SI as a carbonate unless the TA is adjusted as recommended or the alternative would be to drain and or remove (osmosis) the excess CYA down to the recommended level for any pool sanitizing method. I have to admit the information is very compelling.
So going back to my original post regarding my PH stability issues, is this very same scenario of lower levels of carbonates conversly affecting my PH buffering thereby lending to a PH bounce up effect or is the CYA a PH buffer too and not applicable in this scenario or should I then increase my TA level based on the previous informtion with Bicarbonate to compensate as recommended too? Would this do double duty and negate the need to make the TA calculation adjustment for the purpose of the SI results? Well, I don't want to annoy anyone here over this subject but you just have to scratch your head!!!! I also realize this might be unsettling to the Tri-chlor/Di-chlor industry if all this were actually true.
So going back to my original post regarding my PH stability issues, is this very same scenario of lower levels of carbonates conversly affecting my PH buffering thereby lending to a PH bounce up effect or is the CYA a PH buffer too and not applicable in this scenario or should I then increase my TA level based on the previous informtion with Bicarbonate to compensate as recommended too? Would this do double duty and negate the need to make the TA calculation adjustment for the purpose of the SI results? Well, I don't want to annoy anyone here over this subject but you just have to scratch your head!!!! I also realize this might be unsettling to the Tri-chlor/Di-chlor industry if all this were actually true.
cfherrman
TFP Guide
The Taylor water wheel is lsi, or the old junk science
Csi and pool math is new science, and the behind the scenes math that he's talking about
Csi and pool math is new science, and the behind the scenes math that he's talking about
How come the traditional approach is a TA of 80-120+ if higher TA makes pH rise faster and the rationale for a higher TA is that it controls pH fluctuations?
- May 23, 2015
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I am not dismissing anything. What I said is that it is not at all necessary for a pool owner that uses TFP and PoolMath to bother calculating the adjusted alkalinity because the PoolMath app and website already does that. The only thing those tools need are the values you obtain from test kit (FC, CYA, TA, pH, CH, temp, etc) and then the software takes care of the rest. The only time a pool owner needs to lookup corrections to the TA test is when you are using something like the Taylor Watergram where you should be using the adjusted alkalinity. Taylor also uses LSI instead of the more technically rigorous CSI and so you also have to add in corrections for salinity (sometimes generalized as total dissolved solids or TDS). This is the benefit of using TFP and PoolMath, there is no need for correction factors or lookup tables.
As for pH rise, cyanurate alkalinity is not going to help with that. At pH values above 7.0, you are very far away from the cyanurate equilibrium point (pKa ~ 6.5) for the buffering strength of cyanurate / cyanuric acid equilibrium to have much effect. It takes excessively high concentrations of CYA, above 150ppm or more, for it to start to have noticeable effects on the pH change of water above a pH of 7.5. But, more generally speaking, all alkaline species in the water (carbonates, cyanurates, borates, etc) will have some effect on the way in which pH changes through the addition of acids and bases; this is the “buffering effect”, ie, the resistance to change in pH when acids or bases are added to solution. In a previous post I included links to an older thread where chem geek calculated how much acid or base was required to change pH for different combinations of carbonate/cyanurate/borate concentrations. He did this to show that cyanurate alkalinity really only is significant when you add acid to lower pH and that borate alkalinity really is only significant when you try to raise pH; carbonate alkalinity sits in the middle of those two and is the strongest at typical pool pH values (7.2-7.8). It’s a technical post and may not be for everyone but it shows the general principle of how the different chemical species in water will affect pH.
What is misunderstood so often by most people is this point - if the chemical buffering species in the pool water never changed in concentration, then pH would only change when you add an acid or a base and the magnitude of that change would be entirely dictated by the concentrations of those different species and how much acid or base one added. However, that is not the case as there is one chemical species that does change concentration over time - carbonates. Because bicarbonate can transform into dissolved CO2 and because that dissolved CO2 can be released to the atmosphere through the process of outgassing, the carbonate portion of the alkalinity is never constant. CO2 is constantly being lost to the atmosphere through outgassing and it doesn’t take much CO2 outgassing to cause rising pH. If cyanurates or borates were volatile species like carbonates are, then they would cause pH rise too. But, they are not, so they don’t.
This why TFP advises pool owners to try lowering TA and thereby lower carbonate alkalinity as it is the only species that can be released from the water. When you lower TA, you lower the driving force for pH rise and the pH will rise more slowly. In some pools, even with lowered TA, the improvement in acid demand is not spectacular and the pool owner is still stuck with regular acid additions...that’s just life with a pool. Changing CYA levels will have little to no effect on that acid demand. Adding borates can sometimes decrease the frequency of acid additions but the amount of acid needed to move pH increases and so you wind up just adding more acid less frequently. Some people prefer that while others do not.
So why the traditional recommendation for a higher TA (around double TFP's recommendations), given that carbonate->CO2->outgassing is the primary driver of pH rise?
- May 23, 2015
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Those recommendations are mostly the kind of alkalinity levels you find in closed water delivery systems where you want a slightly positive saturation value so that you can keep a healthy layer of scale on the inside of pipes. In a pool, those levels don't make much sense unless you are using acidic forms of chlorine and have low TA fill water. When you have those conditions, then keeping the TA high makes sense because the solid chlorine products are using it up as they dissolve. In pools where water is hard and stabilized chlorine is not used, those levels will only drive pH up. The CPO Training courses cover this somewhat but leave out a lot of details and don't make adjustments for different pool water conditions. It's a "one-size fits all" approach to recommended levels that leads to a lot of confusion and frustration.
So did the pool industry copy TA recommendations (80-120) from other industries, and it became gospel over time, similar to FC of 1-1.5 being "ideal"?
We seem to be drifting away from DrD’s desire to stabilize their pH and reduce acid use again.
- May 23, 2015
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- 16000
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Re: "Adjusted TA" calculation needed for PH stabilization
It's basically borrowed and misapplied science.
- - - Updated - - -
In Arizona, especially Phoenix and Tucson with it's hard water and reliance on surface water supplies, the only way to reduce acid demand is to lower TA to below industry recommended levels (and even TFP recommended levels) and, if allowable, use borates in the water. The trick is too simply keep an eye on the CSI value so you stay in a slight negative range and to keep your pH in the 7.6-7.8 zone. Doing all of that, even with water that has a CH > 1200ppm, I have been able to reduce my acid additions to once every 7-10 days or so. Acid is by far the biggest "consumable" chemical expense for me but, because I use a refillable bulk supplier, it's pretty cheap at $4.75/gallon and I use perhaps 8-10 gallons per year.
If anyone has any other method of reducing acid demand, I'd be more than happy to read about it....however, I'm fairly confident that there is no other cheaper and easier alternative then just using the method that TFP teaches.
It's basically borrowed and misapplied science.
- - - Updated - - -
In Arizona, especially Phoenix and Tucson with it's hard water and reliance on surface water supplies, the only way to reduce acid demand is to lower TA to below industry recommended levels (and even TFP recommended levels) and, if allowable, use borates in the water. The trick is too simply keep an eye on the CSI value so you stay in a slight negative range and to keep your pH in the 7.6-7.8 zone. Doing all of that, even with water that has a CH > 1200ppm, I have been able to reduce my acid additions to once every 7-10 days or so. Acid is by far the biggest "consumable" chemical expense for me but, because I use a refillable bulk supplier, it's pretty cheap at $4.75/gallon and I use perhaps 8-10 gallons per year.
If anyone has any other method of reducing acid demand, I'd be more than happy to read about it....however, I'm fairly confident that there is no other cheaper and easier alternative then just using the method that TFP teaches.